The present invention relates to hindered phenyl compounds, particularly bis-(norbornyl or substituted norbornyl) derivatives of a phenol or a phenylamine, a process for their preparation and compositions containing the bis-(norbornyl or substituted norbornyl) derivatives.
Oxidation of polymeric compositions (e.g., the formation of conjugated double heads in a polymer matrix having carbon to carbon double bonds) is known to deleteriously effect the physical properties of the composition. For example, the tensile strength and physical integrity of various polymeric films or coatings are significantly degraded upon excessive oxidation.
Certain phenols substituted in the 2 and 6 positions (commonly referred to as "hindered phenols") and various 2,6-substituted phenylamines can be employed as antioxidants to protect polymeric materials from oxidation. For example, a di-butyl-para-cresol is widely employed as an antioxidant in a variety of compositions. Unfortunately, large amounts of this material and other hindered phenols or phenylamines having a similarly low molecular weight are generally required to impart the desired antioxidant effect to the compositions. In addition, di-butyl-para-cresol and the like possess relatively high volatilities which make them less practical, from a commercial standpoint, for many applications.
British Patent Specification Nos. 728,290 and 728,291 disclose bis(2-hydroxy-3-.alpha.-alkylcycloalkyl-5-methylphenyl)methanes wherein the cycloalkyl groups are cyclopentyl, methylcyclopentyl, cyclohexyl or methylcyclohexyl as antioxidants. The disclosed compounds melt at relatively high temperatures, e.g., about 120.degree. C. and above. Due to these high melting points, the disclosed antioxidants are not effectively employed in various applications. For example, in the preparation of latex foam backed carpets, a mechanical froth of a polymeric latex composition, a filler and a cross-linking agent for the polymer is deposited on the back of the carpet and subsequently dried and cured at elevated temperatures. Although temperatures of up to and exceeding 140.degree. C. are employed to dry and cure the polymer, due to the evaporation of the water and the heating time required, the latex compositions are generally not exposed, for the required time period, to temperatures sufficiently high to melt the antioxidant and to uniformly distribute it through the latex composition. This results in poorer resistance of the foam backed carpet to oxidation.
An alternative hindered phenol is disclosed as bis(2-hydroxy-3-butyl-5-ethylphenyl)methane. This compound also melts at a relatively high temperature and, upon melting, forms a relatively volatile liquid.
In view of the deficiencies of the antioxidants known to the prior art, it is highly desirable to prepare an effective antioxidant having a relatively low melting ranging from 90.degree. to 120.degree. C. and a desired low volatility.